You asked one question but now I suspect you are really asking about something related:
"Activation Lock for iPhone, iPad, and iPod touch" is a security feature, in part to deter re-selling of stolen devices. To learn more click here --> http://support.apple.com/HT201365
An activation lock can only be removed using the log-in information for the account that applied the lock. If you know this information click on the link to read how to "Turn off Activation Lock." --> https://support.apple.com/HT201441
If you do not know the Apple ID and password and you are not the original owner, get the owner of the account to remove the lock or return the device for a refund. The device is otherwise useless to you. If the owner has not provided contact information as a message showing in the login screen there is no way to contact the owner unless the person who gave you the device knows them.
If you are the original owner and have forgotten the log-in information, try to recover it:
- "If you forgot your Apple ID" [this is likely an email address you are using or used in the past] click here --> https://support.apple.com/HT201354
- "If you forgot your Apple ID password" click here --> https://support.apple.com/HT201487
This really would be the best solution because your account also contains everything else you did through Apple, it doesn't just give you access to this device.
Otherwise:
Apple may possibly remove a lock if a person can provide sufficient evidence of valid ownership. The device is normally taken to an Apple Store with identification and the original sales receipt. I.e., the receipt when the item was sold to the first owner, and preferably by that person. This is unofficial and there is apparently no set policy (I asked at an Apple Store). A store may simply refuse, particularly if they are not satisfied you have proven ownership by provenance. I suspect you would also end up losing access to your Apple ID.
